A well owner must be alert for any change in the appearance or taste of the water, for this indicates possible contamination. Sometimes the laboratory examination of a water sample reveals bacteriological contamination.

Under any of these conditions, all water used for drinking or food processing and cooking should first be boiled or disinfected or treated as approved by the health department, until the cause of the change in quality or contamination is found and removed. Where a public water supply becomes available, it should be used, and the polluted well filled in (Consult AWWA standard A100 for directions) or the water made inaccessible. If a new well is drilled, it should be located, constructed and protected as explained in this booklet.

Finding the cause. A sanitary survey of the surrounding area should be made to find the probable cause of pollution. If a sewage disposal system is near the well, a dye or ordinary salt flushed down the kitchen sink or toilet bowl may show in the well. Detergent used in the kitchen or home washer may find its way into the well and appear as foam in tap water.

Polluted surface water or superficial ground water immediately around the well can also enter the well through holes in the side of the casing, channels along the length of the casing, or crevices in the rock leading to the well. Sometimes the casing is loose or is only a few feet long. An inspection should be made of the top and inside the casing, using a mirror or strong light, to determine if water is entering the well from close to the surface or through the bottom of the casing.

A dye or salt solution, or even plain water, poured around the casing can help reveal the source of pollution. A chemical examination may be needed to show the change in the chlorides or the presence of dye in the water if the salt cannot be tested nor the dye seen.

Correction. If the casing is not tight, a competent well driller can investigate the possibility of sealing the opening, installing a properly sealed inner casing, providing a sanitary well seal for the pumpline at the casing, or sealing a new casing carefully in rock with cement grout.

If the casing is found to be tight, it is assumed that pollution is finding its way into the water-bearing stratum through sewage saturated soil or creviced rock or channeled rock (limestone) at a greater depth. Sometimes the polluted stratum can be sealed off and if necessary the well drilled deeper. But there is no guarantee of water or that the new formation will not become polluted later. Check the cost and advisability for doing this with a competent well driller and a geologist.

Once a stratum is contaminated with sewage, it is very difficult to prevent future pollution of the well unless all water from such a stratum is effectively sealed off. Moving the offending sewage disposal system to a safe distance is possible, but evidence of the pollution may persist for some time. The same general principles apply to dug and driven wells.

In an emergency, contaminated well water or surface water can be made satisfactory for drinking by boiling or by chemical disinfection. The water should be as clear as possible; let muddy or cloudy water settle, then pour off the clear water into a separate container. Filtering the water through a clean cloth or milk strainer may help.

When heat or fuel is available, the safest way to make a small volume of water satisfactory for drinking is to boil it for at least two minutes. The water should then be cooled and stored in a clean protected container.

Chemical disinfection of clear water is summarized below. If the water is turbid or colored, double the amount of disinfectant.